The present invention relates to a substrate treating method for drying a coating solution on a substrate by heating when predetermined treatment is performed for the substrate coated with the coating solution such as an LCD substrate, a semiconductor wafer or the like.
In the fabrication of a liquid-crystal display (LCD), for example, a circuit pattern is formed by so-called photolithography technology in which a rectangular glass LCD substrate (referred to as a substrate hereinafter) is coated with a coating solution such as a photo-resist solution to form a resist film and in which the resist film is exposed correspondingly to the circuit pattern and developed.
In the process of coating a resist solution, in order to enhance the fixedness of the resist, the rectangular substrate is given hydrophobic treatment in an adhesion treating unit and cooled in a cooling unit, and then carried in a resist coating unit.
In the resist coating unit, while the rectangular substrate is rotated in the state of being held on a spin chuck, a resist solution is supplied to the central portion of the surface of the substrate from a nozzle provided above the central portion and spread by centrifugal force due to the rotation of the substrate, whereby the entire surface of the substrate is coated with a resist film.
After an excess resist at the periphery of the substrate is removed, the substrate coated with the resist solution is carried in a heating unit to undergo pre-baking treatment. In the heating unit, in order to prevent direct contact of a heating plate and the substrate, a so-called proximity type is often adopted in which the substrate received by lifting pins is mounted on securing pins of the heating plate and heated by heat radiated from the heating plate.
Subsequently, the substrate is cooled in a cooling unit and carried to an aligner where a predetermined pattern is exposed. Thereafter, the substrate is developed and given post-baking treatment, thereby forming a predetermined resist pattern.
In the above coating and developing unit, however, there are some cases where shapes of the lifting pins, securing pins, vacuum grooves, or the like are transferred to the substrate after the substrate coated with the resist solution receives pre-baking treatment and the like, or after the substrate is exposed and developed.
The transfer of the lifting pins and the like is caused specifically by the film thickness of the resist solution coated on the substrate being changed correspondingly to the shapes of the lifting pins and the like after pre-baking treatment, and by the line width of the circuit pattern formed on the substrate being changed according to the shapes of the lifting pins and the like after exposure and development. Even when no transfer is found after pre-baking treatment, there are cases where transfer occurs after development.
It is supposed that such transfer is caused by a sensitized resist solution being used recently and by the line width of a circuit pattern formed on an LCD substrate being 3 xcexcm which is smaller than ever, but the cause thereof is not determined in detail. Hence, success is not achieved yet in preventing such transfer.
As described above, however, such transfer of the lifting pins and the like corresponds to the ununiformity of the film thickness of the resist solution and a change in line width of the circuit pattern. Thus, it is requested to prevent to the utmost such transfer from occurring on the substrate in the coating and developing process of the LCD substrate.
The present invention is made in view of the aforesaid disadvantage, and its object is to provide a substrate treating method capable of preventing transfer which is indexes of ununiformity of film thickness of a resist solution and change in line width of a circuit pattern.
In order to solve the above disadvantage, according to the first aspect of the present invention, a substrate treating method for performing predetermined treatment for a substrate coated with a coating solution including the steps of (a) heating the substrate coated with the coating solution at a first predetermined temperature, (b) lowering the temperature of the substrate by positively cooling the substrate and/or by naturally releasing the heat thereof after the step (a), and (c) heating the substrate at a second predetermined temperature after the step (b) is provided.
In the non-heated step (b) in the substrate treating method according to the first aspect, it is possible that the substrate is carried out of a heating unit, that is, the temperature of the substrate is lowered by natural heat release and/or that the substrate is positively cooled by a cooling unit.
Further, preferably the first predetermined temperature in the heating step (a) is lower than the second predetermined temperature in the heating step (c). Therefore, when the heating step (a). and the heating step (c) are performed in the same treating unit, preferably a space between the substrate and a heating plate in the heating step (a) is larger than that in the heating step (c).
According to the second aspect of the present invention, a substrate treating method for performing predetermined treatment for substrates coated with a coating solution including the steps of (a) heating the substrates coated with the coating solution one by one at a first predetermined temperature, (b) lowering the temperature of the substrates by positively cooling the substrates and/or by naturally releasing the heat thereof one by one after the step (a), (c) heating the substrates one by one at a second predetermined temperature after the step (b), (d) lowering the temperature of the substrates by positively cooling the substrates and/or by naturally releasing the heat thereof one by one after the step (c), and (e) heating the substrates one by one or plural substrates at a time at a third predetermined temperature after the step (d), is provided.
In the non-heated step (b) and the non-heated step (d) in the substrate treating method according to the second aspect, it is possible that the substrate is carried out of the heating unit, that is, the temperature of the substrate is lowered by natural heat release and/or that the substrate is positively cooled by the cooling unit.
Further, preferably the first predetermined temperature in the heating step (a) is lower than the second predetermined temperature in the heating step (c), and preferably the second predetermined temperature in the heating step (c) is lower than the third predetermined temperature in the heating step (e).
Furthermore, in the heating step (e), similarly to the heating steps (a) and (c), the substrates may be heat-treated one by one, or the plural substrates may be concurrently heat-treated in one treating unit, for example, a heating furnace or the like in order to enhance throughput of treatment.
According to the substrate treating method in accordance with the first and the second aspects, the heating step (a) can be performed before exposing the substrate, and the heating step (c) can be performed after exposing the substrate.
Moreover, predetermined treatment for the substrate, for example, drying treatment while supplying gas, drying treatment under reduced pressure, gelling treatment of a coating film, exchanging treatment of a coating film solvent after coating the solvent, removing treatment for removing at least a part of a coating film, or the like may be performed before the heating step (a) or between the heating step (a) and the heating step (c).
According to the third aspect of the present invention, a substrate treating method for performing predetermined treatment for a substrate coated with a coating solution including the steps of (a) heating the substrate coated with the coating solution, and (b) putting the substrate in a non-heated state after said step (a), with the steps (a) and (b) being repeated a plurality of times, is provided.
In the non-heated step (b) in the substrate treating method according to the third aspect, it is possible that the substrate is carried out of the heating unit, that is, the temperature of the substrate is lowered by natural heat release and/or that the substrate is positively cooled by the cooling unit.
With the repetition of the heating process and the non-heated process a plurality of times, it is preferable that the treating temperature in the heating process is set at higher temperature.
Further, predetermined treatment for the substrate, for example, drying treatment while supplying gas, drying treatment under reduced pressure, gelling treatment of a coating film, exchanging treatment of a coating film solvent after coating the solvent, removing treatment for removing at least a part of a coating film, or the like may be performed before the heating step (a) or between the heating step (a) and the non-heated step (b).
According to the first and the second aspects of the present invention, the substrate coated with the coating solution is heated at the first predetermined temperature, and after the above heating, through the non-heated step (b), the substrate is heated at the second predetermined temperature. According to the third aspect, the step of heating the substrate coated with the coating solution and the step of putting the substrate in a non-heated state are repeated a plurality of times, thus gradually releasing a solvent in the coating solution, promoting drying of the coating solution without exerting a bad influence on the coating film, and effectively preventing the occurrence of transfer on the substrate.
Further, in the first and the second aspects, a heating temperature in the heating step (a) is made lower than that in the heating step (c), thus holding down abrupt vaporization of the solvent in the coating solution to provide a more appropriate dried state and more effectively preventing the occurrence of transfer. The above difference in temperature can be realized by providing a low-temperature heating unit and a high-temperature heating unit both of which are different in set temperature, and by setting a space between the substrate and a heating plate in the heating step (a) larger than that in the heating step (c).